This application is for support of a new experimental program in which two laboratories with expertise in different disciplines, Cellular Electrophysiology and Biophysics, and Cartilage Tissue Engineering, will collaborate to study CHONDROCYTE MECHANOBIOLOGY. Principles of Physiology, Cell Biology, and Tissue Engineering will be used to identify novel mechanisms of mammalian chondrocyte function, and to relate these to the responses of healthy and compromised joint tissue. Recent results from pilot studies provide the rationale and establish feasibility: i) Novel electrophysiological characteristics of acutely isolated mammalian chondrocytes have been identified in the Giles lab. ii) In the Sah lab, experiments on explanted slices of tissue have revealed milieu-specific changes in chondrocyte metabolism, and genetic programming. Our OVERALL HYPOTHESIS is that CHONDROCYTE MEMBRANE POTENTIAL can modulate function e.g., EXCITATION-SECRETION COUPLING. The Specific Aims include: 1. Application of conventional and perforated patch electrophysiological methods to study the K+ and Clcurrents which are responsible for the membrane potential in acutely isolated bovine chondrocytes. These studies will be done under control conditions or in the setting of physiological perturbations, including +/- 20% changes in osmotic strength, and alterations in pH. [unreadable] 2. Determination of the extent to which chondrocytes isolated from selected regions (depths) of joint tissue exhibit electrophysiological heterogeneity. [unreadable] 3. Simultaneous measurements of membrane potential and [Ca2+]i or pH in explanted tissue slices which can be subjected to controlled, graded mechanical stresses similar to those in mammalian joints. These studies will provide a new, multidisciplinary research and training opportunities for Basic Scientists, and Clinician Scientists. [unreadable] [unreadable]